Aluminium Alloys

ALUMINIUM ALLOYS

✓ At room temperature, the mechanical properties of aluminium alloys are:

(i) interior to those of steel;

(ii) almost equal to those of copper alloys; and

(iii) superior to those of magnesium alloys.

✓ The aluminium may be alloyed with one or more alloying Isot elements such as Cu, Mg, Mn, Si, and Ni.

✓ The addition of small amounts of alloying elements convert the soft and weak aluminium metal into hard and strong one, while retaining its light weight property.

1. Types of Aluminium Alloys

The alloys of aluminium may be subdivided into two groups↑ as: 

1. Heat-treatable aluminium alloys, and

2. Non-heat treatable aluminium alloys.

1. Heat-treatable aluminium alloys

✓ The heat-treatable alloys cannot be strengthened by using a special type of heat treatment such as age hardening or precipitation hardening.

✓ The principal heat-treatable aluminium alloys are :

1. Al-Cu alloys,

2. Al-Cu-Ni alloys,

3. Al-Mg-Si alloys,

4. Al-Zn-Cu alloys, and

5. Al-Li alloys.

† Aluminium alloys can also be divided into two groups, depending on their methods of fabrication, as :

1. Wrought alloys: They are used in the wrought form, i.e., they are rolled to sheet, strip or plate; drawn to wire; or extruded as rods or tubes.

2. Cast alloys: They are cast to shape by either a sand-casting or a die-casting process.

2. Non-heat treatable aluminium alloys

✓ These alloys may be strengthened by cold working operations.

✓ The important non-heat treatable aluminium alloys are:

1. Al-Mn alloys,

2. Al-Mg alloys, and

3. Al-Si alloys

However, our study is limited to only Al-Cu alloy system.

2. Al-Cu Alloys

The two important Al-Cu alloys are :

1. Duralumin, and

2. Y-alloy.

Table 3.23 presents compositions, properties, and typical applications of these two Al-Cu alloys.